ホメピゾール
**ホメピゾール**（別名4-メチルピラゾールまたは4-MP）は、主に犬や猫の**エチレングリコール（不凍液）中毒**の治療に使用される合成解毒剤です。 臨床上の重要なポイント： * **時間的制約**：犬の場合、摂取後8時間以内に投与すれば非常に効果的です。猫の場合はかなり高用量が必要であり、致命的な腎損傷を防ぐために摂取後3時間以内に投与する必要があります。 * **作用機序**：元の化合物を除去するのではなく、有毒な代謝物の形成を防ぎます。 * **臨床的真珠**：高窒素血症（腎数値の上昇）が発症すると予後は急激に悪化しますが、血液透析などの支持療法を開始する間、さらなる損傷を食い止めるために摂取後最大36時間までホメピゾールを投与することができます。 * **費用と入手可能性**：特に大型犬の場合、治療費が非常に高額になる可能性があり、救急現場では薬の迅速な入手が制限要因となることがよくあります。
作用機序: Fomepizole acts as a potent, competitive inhibitor of **alcohol dehydrogenase (ADH)**, the primary enzyme responsible for the initial metabolism of ethylene glycol. **The Toxic Pathway:** Ethylene Glycol → (via **ADH**) → Glycoaldehyde → Glycolate → Glyoxalic Acid → Oxalic Acid. *Note: Oxalic acid binds with systemic calcium to form calcium oxalate crystals, which precipitate in the renal tubules causing acute tubular necrosis and severe metabolic acidosis.* **Fomepizole's Action:** By competitively binding to **ADH** with an affinity roughly 8,000 times greater than that of ethylene glycol, fomepizole effectively blocks the first step of this cascade. * Ethylene glycol remains unmetabolized in the bloodstream. * The parent compound (which is only mildly CNS-depressant) is then safely and slowly excreted unchanged in the urine. * This prevents the life-threatening metabolic acidosis and acute kidney injury associated with the toxic metabolites.
動物種別の用量
- For treatment of ethylene glycol toxicity · Initially, 125 mg/kg slow IV ; at 12, 24, 36 hours give 31.25 mg/kg IV . · IV · Specific intervals (0, 12, 24, 36 hours) · 36 hours · Cats must be treated within 3 hours of ingestion. Treat supportively with supplemental fluids. Cats whose treatment began 4 hours post ethylene glycol had 100% mortality.
- For treatment of ethylene glycol toxicity · Initially load at 20 mg/kg IV ; at 12 hours post initial dose give 15 mg/kg IV ; at 24 hours post initial dose give another 15 mg/kg IV and at 36 hours after initial dose give 5 mg/kg; may give additional 5 mg/kg doses as necessary · IV · Specific intervals (0, 12, 24, 36 hours) · 36+ hours · May give additional 5 mg/kg doses as necessary if animal has not recovered or has additional ethylene glycol in blood.
用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。
投与経路
禁忌
- No labeled contraindications, but use with caution if the patient is already receiving ethanol therapy.
有害事象
- Vein irritation and phlebosclerosis (if given rapidly or undiluted)
- Anaphylaxis (rare)
- Mild sedation (particularly in cats)
薬物相互作用
- Ethanol · Fomepizole inhibits alcohol dehydrogenase; ethanol metabolism is reduced significantly and alcohol poisoning (CNS depression, coma, death) can occur. Concurrent use is generally not recommended. If used together, mandatory monitoring of ethanol blood levels is required.
モニタリング
- Ethylene glycol blood levels (to document diagnosis and determine if therapy can be discontinued after 36 hours)
- Blood gases (acid-base status)
- Serum electrolytes
- Hydration status
- Renal function tests (Urine output, urinalysis, BUN, serum creatinine)
- Body temperature (especially in cats)
過量投与
Overdosage may cause significant **CNS depression**. There is no specific antidote or treatment recommended for fomepizole overdose; provide supportive care as needed.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。